Serum 99th centile values for two heart-type fatty acid binding protein assays

Background: We have previously demonstrated that heart-type fatty acid binding protein (H-FABP) is an independent prognostic marker for survival after acute coronary syndrome (ACS). This study aimed to define the 99th centile values for H-FABP as determined with two different assays, and to study the relationship with age, gender and renal function. Methods: H-FABP was measured on redundant routine outpatient samples using the MARKIT-M (Dainippon) and the Evidence Investigator (Randox) assays. Results: Two hundred and forty-two subjects with Siemens Ultra-Tnl value <0.045 mu g/L (99th centile) were studied. In all, 174 subjects had estimated glomerular filtration rate (eGFR) >60 mL/min. The 99th centile values for subjects with eGFR >60 mL/min for the Evidence Investigator H-FABP were 5.3 and 5.8 mu g/L and for the MARKIT-M H-FABP were 8.3 and 9.1 mu g/L in female and male subjects, respectively. There is an increase in H-FABP with age in subjects with normal renal function for both assays. Gender comparison showed no significant difference for either assay. Comparison of samples showed that subjects with eGFR <60 mL/min showed a median increase of 0.71 mu g/L with Evidence Investigator assay and 1.09 mu g/L with MARKIT-M assay compared with subjects with eGFR >60 mL/min. Calibration differences were confirmed by cross measurement of calibrators and recombinant H-FABP. Conclusions: We have defined the 99th centile values for H-FABP in a population of primary and secondary care outpatients that can be used to risk stratify patients with ACS. We have confirmed that H-FABP increases with renal dysfunction and age, but have not confirmed the gender difference previously reported.